Instructions:
Combine the coconut milk and water. Stir until smooth. Add the sugar and cornstarch. Cook over low heat until thickened and shiny. If the haupia is grainy, you need to keep cooking the mixture because the fat in the coconut milk has not yet melted.

* You can make your own coconuit milk by mixing equal amounts of shredded coconut and water, simmer until foamy, then strain the mixture through cheesecloth, squeezing as much liquid out of the pulp as possible.

Great idea on the Spam! How about some simple Spam musubi? Most of the Spam musubi has the Nori (seaweed) wrapped on the outside but you can do something like this and just add the Nori on top before you serve it. This will prevent the nori from getting soggy and yucky.

You can make everything the night before. Slice the Spam about 1/2" thick slices. I would recommend pan frying the Spam just until the sides are getting brown. Then use a small round cookie cutter to get the rice and the Spam the same size. Fairly simple and cheap!

BTW, I love loco moco when it's done right. I make that every-so-often at home for lunch but prefer using my fried rice with Portugese sausage. I don't know how easy it would be to make loco moco for a pot luck, though. It's not a standard flare at a luau.